This invention relates to vehicle length sensors, typically but not exclusively for vehicles such as may have variable length, and to a vehicle being provided with such a sensor.
The correct and quick determination by a driver of a vehicle of whether there is another vehicle alongside their vehicle is both essential for modern highway driving and is also potentially hazardous, particularly in situations where the driven vehicle has to change lanes, such as in an overtaking manoeuvre or when joining a highway. A vehicle may be in the blind spot—the area alongside the vehicle that cannot be viewed from the rear view mirrors of a vehicle. Even with a vehicle in the area visible in the rear view mirrors, a driver may be unable, be it through lack of skill, poor visibility or even through simply not having looked, to determine how close a vehicle is in an adjacent lane. This is particularly a problem with variable length vehicles, such as trucks, which can pull trailers of different lengths or numbers.
Blind spot detectors have been proposed which detect whether there is a vehicle immediately in the blind spot of the vehicle. However, they do not help a driver judge whether there is sufficient space to move into a given lane. Lane change assist detectors have also been proposed, which determine whether there is a fast-approaching vehicle in an adjacent lane; such detectors are more concerned with alerting a driver to a potential, rather than a present problem.